Teletypewriter switching system



April 8, 1941. H. J. BRITT TELETYPEWRITER SWITCHING SYSTEM Filed Dec. 3, 1938 I ,C L.

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Patented Apr. 8, 1941 UNITED STATES PATENT OFFICE TELETYPEWRITER SWITCHIN G SYSTEM Application December 3, 1938, Serial No. 243,866

(Cl. 178-2l 10 Claims.

This invention relates to a printing telegraph selective switching system and, more particularly, to a teletypewriter switching system having means for permitting messages from a transmitting teletypewriter station to be automatically routed to one or the other of two receiving teletypewriter stations.

Certain types of teletypewriter service, such as a dispatching system for the transmission of orders or accounting information, involve the transmission of a large number of short messages from a central teletypewri'ter station to one or the other of two receiving teletypewriter stations. Ii manual switching systems were employed for this service, the lines would need to be multiplied to several operators and the messages would have to be sorted and grouped in order to avoid more than one operator attempting to use a particular transmission line. This would result in an uneven distribution of the work unless there were the same number of messages for each receiving station.

Accordingly, it is an object of this invention to provide a teletypewriter switching system with means for automatically routing messages to one or the other of two receiving teletypewriter stations.

It is also an object of the invention to disconnect a connected receiving teletypewriter station without the use of a special, or extra, disconnect signal.

It is a further object of the invention to provide means under the control of a transmitting teletypewriter for connecting it to a rec-eiving teletypewriter station while disconnecting it from another receiving teletypewriter station.

A modification of the invention permits a teletypewriter subscriber to disconnect his teletypewriter from one receiving teletypewriter station and connect it to another receiving teletypewriter station by transmitting from his teletypewriter a plurality of preassigned permutation code sig nals and enables him to switch his teletypewriter back to the iirst receiving station by transmitting the same permutation code signals but in reverse L order.

These and other objects of the invention are accomplished by providing a central, or switching, teletypewriter with a platen contact and two pull bar contacts of the type described inPatent 2,120,235 granted June 14, 1933 to J. F. Beattie et al. The disclosure of this Beattie et al. patent is incorporated herein by reference as a part of this specification. To accomplish the objects of this invention, the platen contact and the twopull bar contacts are employed for controlling the energization of -switching relays. Operation of the platen contact and one pull bar contact causes the switching relays to operate their armatures to contact the transmitting teletypewriter station to one of the receiving stations, the switching relays locking-up over a path controlled by another relay. Operation of the platen contact and the other pull bar contact causes this last-mentioned relay to open the locking-up circuit of the switching relays` which release their armatures to disconnect the previously connected receiving station and to then connect the transmitting station to the other receiving station.

To prevent switching operations from being unintentionally performed by line hits or unintentional sending of the switching signals, a modification of the invention comprises the use of additional relays whereby one station is switched to the transmitting station in response to the operation of the platen contact and both of the pull bar contacts. This station is disconnected and the other station is connected to the transmitting station in response to the operation of the platen contact followed by the operation of both of the pull bar contacts in an order which is the reverse of that in which they were first operated.

These and other features oi the invention are fully described and explained in connection with the following detailed description of the drawing in which:

Figure 1 is a schematic circuit diagram of the selective teletypewriter switching system; and

Fig. 2 is a similar circuit diagram of the modined switching system.

In Fig. 1, a subscribers transmitting teletypewriter station A is shown to be connected by a transmission line L1 to a teletypewriter central office l to which two other subscribers teletypewriter stations, stations B and C, are connected by transmission lines L2 and L3, respectively. The central oice I is provided with a teletypewriter T4 which may be of the type disclosed in Patent 1,745,633 granted February 4, 1930 to S. Morton et al. The disclosure of this Morton et al. patent is incorporated herein by reference as a part of this specification. Teletypewriter T4 is providedwith a platen contact 2 which is opened and closed under the control of a lever 3 which is also used for shifting the platen (not shown) of teletypewriter T4 in the manner described in the above-mentioned Morton et al. patent. Teletypewriter Ti is further provided with two contacts 4 and 5 operated respectively by pull bars B and l. These pull bars [i and 1 are preferably those which have little used upper case symbols, such and 8i which are the upper case symbols for the J pull bar Ii and the G pull bar l, respectively. Teletypewriter T4 is permanently connected in series with the teletypewriter T1 at station A so that it will always be readily available to perform the desired switching functions.

With the circuit in the condition shown in Fig. 1, the subscriber A is shown to have his teletypewriter T1 connected in series over line L1 to the teletypewriter T4 at the central ofce I and also to the teletypewriter T2 at station B. This communication path leads from station A over the bottom part of line L1 to teletypewriter T4 at the central oiiice I, over break key sending contacts 9, printer magnet I0, and then along conductor I I to the lower bottom contact of switching relay I2. From this point, the path extends over conductor I3 to the bottom part of line L2 and then to station B where it passes through the subscribers teletypewriter T2 and then goes back to the central oflice I over the top part of line L2. At the central oiiiee I, the communication path follows conductor I-'I to the upper top contact of relay I2 and then goes out over the top part of line L1 to station A, thus completing the communication circuit. During this time, station C has its teletypewriter T3 connected over line La and conductors 25, 3U, 2l, and Si to batteries 28 and 29 at central oflice I. relays are unenergized.

When the subscriber at station A has a message for the subscriber at station C, he precedes the message with a conditioning, or activating, signal and a routing signal. preferably a certain preassigned permutation code signal, such as a shift signal, the transmission and reception of which cause the platen lever 3 to be operated counter-clockwise to place the platen in its upper case position in the manner described in the above-mentioned Morton et al. and Beattie et al. patents. If the platen should already be in its upper case position, it would not be necessary to send a shift signal at this time. Whenever the platen lever 3 is operated to place the platen in its upper case position, it closes the platen contact 2 which remains closed until an unshift signal is transmitted for moving lever 3 clockwise to the position shown in Fig. 1, thereby restoring the platen to its lower case position and opening contact 2 in the manner described in the Beattie et al. patent.

With contact 2 now closed, the subscriber at station A transmits the routing signal which in the preferred embodiment of the invention is the preassigned permutation code signal for eiTecting the operation of the J pull bar 6 which momentarily closes contact Il. This completes a path from ground I 5, Contact 2, conductor i6, contact 4, and then along conductor Il to junction I8. Here the path divides, one-half going through relay I 2 to battery I 3 and the other through relay 2li to battery I9. This energizes the switching relays I2 and 20 which operate their armatures and lock-up over a path from battery I9, through the windings of relays I 2 and 20 to junction 2|, over the bottom operated armature of relay 29, conductor 22, and then over the non-operated armature of relay 23 to ground 24. Relays I2 and 2i! are designed to be quick-acting so that they will operate and lockup before the pull bar contact 4 opens.

The operation of the armatures of the switching relays I2 and 20 switches station B out of the transmission circuit and switches station C into the transmission circuit in the following manner.

At this time, all the Y The conditioning signal is i Cil The operation of the outer top armature of relay I2 opens the path from the upper part of line L1 to conductor I4 and closes the path from line L1 to conductor 25 leading over line La to station C. The operation of the outer bottom armature of relay i2 opens the path from the lower part of line L1 to conductor I3 and transfers it to conductor 26 leading over conductor 2l' and the lower part of line L3 to station C. At the same time, the inner top and bottom armatures cf relay l2 operate to disconnect batteries 28 and .'9 from conductors 3l] and SI, respectively, both of which lead to station C. Station C is thus switched from batteries 28 and 2S to communicative relation with station A. The outer top and inner top armatures of relay 2U operate to connect batteries 32 and 33 over conductors 3H and 35, respectively, to conductors I4 and I3 leading over line L2 to station B This switches station B out. of the transmission circuit and leaves it in an idle condition connected to batteries 32 and 33.

The entire circuit is now in condition for messages to be transmitted between the subscribers at stations A and C, the communication path being traced from the teletypewriter T1 at station A, over the lower part of line L1, through the central oiiice switching teletypewriter T4, over conductor II, operated outer bottom armature of relay I2, conductors 25 and 2l, over the lower part of line La, through the teletypewriter T3 at station C, back over the upper part of line L3, along conductor 25, over the outer top operated armature of relay I2, and then over the upper part of line L1 to station A. If the rst message begins with an upper case character, no unshift signal is sent. However, if the first message is to begin with a lower case character, the subscriber at station A must transmit an unshift permutation code signal which will cause lever 3 to rotate clockwise and thereby allow Contact 2 to open.

Later, when the subscriber at station A has finished his communication with the subscriber at station C and wishes to resume communication with the subscriber at station B, he transmits a shift signal to operate the platen lever 3 which not only places the platen in its upper case position but also closes the platen contact 2 to conditionthe switching apparatus for operation. Ii the platen of the teletypewriter T4 should already be in its upper case position, it would not be necessary for subscriber A to send a shift signal at this time. However, as a safety precaution, he would usually adopt the routine of preceding a routing signal with a shift signal to insure that contact 2 will be closed to condition the switching circuit for effective operation when a routing signal is transmitted.

The subscriber at station A next transmits the preassigned permutation code signal for operating the G pull bar 'I which closes its contact 5 momentarily in the manner described in the above-mentioned Beattie et al. Patent 2,120,235. This completes a path for current to pass from grounded battery 36, through the winding of relay 23, contact 5, conductor I, contact 2 and then to ground i5, thereby energizing relay 23. Relay 23 operates its armature to remove ground 24 from the locking-up circuit of relays I2 and 28, which consequently, release their armatures.

The release of the outer top and outer bottom armatures of relay I2 disconnects station C from communicative relation with station A while the inner top and inner bottom armatures of relay I2 connect station C over conductors 3i) and 3| to batteries 20 and 29, respectively. At the same time, the two top armaturesof relay 20 disconnect batteries 32 and 33 from station B while the outer top and outer bottom contacts of relay I2 connect conductors I3 and I4 to line L1 leading to station A. Thus, station C' is placed in an idle condition connected to batteries 28 and` 29 while station B is again connected into communicative relation with station A. This switching procedure may be repeated as often as desired. It is t be understood that, although stations B and C have been shown to be provided with sending-receiving teletypewriters T2 and T3, they may, if desired, be provided with receiving-only teletypewriters. switching teletypewriter T4 to be located at a teletypewriter central oince I, it is to be understood that this is the preferred embodiment oi the invention and that it is within the scope of the invention to dispense with a teletypewriter exchange central office and to employ instead a private wire system in which the switching teletypewriter T1 and relays I2, 20, and 23 would be located at station A which would be connected directly to stations B` and C by two private wire the possibility of unintentional operation of the switching apparatus.

The circuit shown in Fig. 2 is somewhat similar to that shown in Fig. 1 except that three control relays |4|, |42, and |43 and their related circuit connections have been added. The circuit illustrated in Fig. 2 is represented as being in a condition analogous to that of the circuit shown in Fig, 1 in that the subscriber at station A1 has his teletypewriter T5 connected to the central oiiice |0| by line L4 and then over conductors 1|4, and ||3 to line Le leading to the teletypewriter Ts at station B1. Thus, stations A1 and B1 are shown to be connected into communicative relation while station C1 has its teletypewriter T v connected over line Ls and conductors |25, |30, |21, and |3| to batteries |20 and |29 at central oflice |0|. All the relays are unenergized at this time.

To reverse this connection, the subscriber at station A1 transmits the preassigned permutation code signal for effecting the operation of the l signed code signal for operating the J pull bar |00 which momentarily closes its contact |04 to complete a path for energizing relay |41. This path is traced from grounded battery |44, through the winding of relay |4I, outer bottom contact and bottom armature of relay `|42, conductor |45, contact |04, conductor ||6, contact |02, and then to ground H5. Accordingly, relay |1t| operates its armatures and locks-up over a path from grounded battery |44, winding of relay |41, bottom armature of relay |41, and then over the non-operated outer top armature of relay |42 to ground |43. At the same time, the top armature of relay |4| prepares a circuit leading from grounded battery ||9, through the windings of relays ||2 and |20 to junction lit.l and. then down conductor |41 to junction |40, conductor |40, operated top armature of relay |41, inner top armature of relay |42, and then along conductor |50 to the open contact |05.

The subscriber atl station A1 next transmits the f Likewise, although Fig. 1 shows the preassigned permutation code signal ior operating the G pull bar |01 which momentarily closes its contact |05 to complete the circuit just traced for applying ground ||5 to battery |I0. Closure of contact |05 also momentarily closes a path from battery I I9, conductor |5|, winding of relay |42, along conductor |52 to junction |48, conductor |49, top armature of relay 14|, inner top armature of relay |42, conductor |50, contact |05, conductor |6, and then to ground i5, thereby operating relay |42.

Before contact |05 opens, relays ||2, |20 and |42 operate and lock-up over a circuit extending from junction |3 to junction |2|, over the inner bottom armature of relay 120, conductor |22, and then over the armature of relay |23 to ground |24. When relay |42 operated its outer top armature, it disconnected ground |46 from relay |4|, thereby opening the locking-up circuit of relay |4| and causing it to release its armatures. At the same time, the inner top armature of relay |42 opens the path from contact |05 to the top armature of relay |4| and prepares a circuit leading from contact |05 over this armature of relay |42, conductor |53, winding of relay |43, and then to grounded battery |54 but contact |05 opens before relay 143 can operate at this time. `The bottom armature of relay |42 operates to prepare a circuit leading from contact |04 to the top armature of relay |43 The operation of the two top armatures of relay switches station B1 to batteries |32 and |33 via conductors |34 and |35. At the same time, station C1 is connected into the transmission circuit via conductors and |25 and the outer top and outer bottom operated armatures of relay ||2. The circuit is thus placed in condition for the subscriber at station A1 to communicate with the subscriber at station C1.

When subscriber A1 wishes to again communicate with subscriber B1, he transmits the activating signal to cause platen lever |03 to close contact |02. The subscriber A1 then transmits the preassigned permutation code signal for operating the G pull bar |01 to close momentarily contact |05 thereby completing the energizing circuit for relay |43. This energizing circuit extends` from ground 1|5, through contact |02, conductor H6, contact |05, conductor |50, inner top operated armature of relay |42, conductor |53, winding of relay |43, and then to grounded battery |54. Relay |43 locks-up over its bottom armature, conductor |55, the outer bottom operated armature of relay |20, and then to ground |55. The top armature of relay |43 prepares an energizing path for relay |23 from battery |35 over the bottom armature of relay |42 and conductor |45 to contact 104.

Subscriber A1 next transmits the preassigned code signal to effect the operation of the J pull bar |06 which closes its contact |04 momentarily and thereby completes the energizing path for relay |23 from battery |36, winding of relay |23, top armature of relay |43, bottom armature of relay |42, conductor |45, contact |04, conductor IIE, contact |02, and then to ground ||5. Accordingly, before contact |04 opens, relay |23 operates its armature which opens the locking-up circuit of relays ||2, |20, and |42 and causes these relays to release their armatures. The release of the two top armatures of relay |20 disconnects station B1 from batteries |32 and |33. The release of the inner bottom armature of relay |20 further opens the locking-up circuit of these relays While the release of its outer bottom armature opens the locking-up circuit of relay |43, which accordingly, releases its armatures. The release of the armatures of relay i2 connects station B1 into the transmission circuit by closing the paths from conductors ||3 and ||4 to line L4 and, at the same time, these armatures disconnect conductors |25 and |26 from line L4 and switch station C1 over conductors |30 and |3| to batteries |28 and |29. Relay |42 releases its armatures thus restoring the entire circuit to the condition shown in Fig. 2.

This procedure can be repeated by the subscriber at station A1 as often as desired. All that he need do to disconnect his station from communicative relation with the subscriber at station B1 and to connect it to station C1 is to transmit a shift signal followed by the preassigned code signals for J and G. To disconnect his teletypewriter T5 from communicative relation with the teletypewriter T7 at station C1 and to connect it to the teletypewriter T6 at station B1, he simply transmits a shift signal followed by the permutation code signals for G and J. In other words, by preceding messages with the proper combination of preassigned permutation code signals, they will be automatically routed to one or the other of the two receiving stationsI B1 and C1.

The invention has been described with reference to its preferred embodiment and its preferred application. It is to be understood that the invention is capable of other applications and may be embodied in other forms and apparatus than that specifically shown in the drawing. Consequently, the invention is not to be limited to the particular form and use shown and described, but is to be limited only by the claims appended hereto.

What is claimed is:

1. A printing telegraph system including in combination a plurality of subscribers printing telegraph stations each provided with a teletypewriter, a plurality of communication channels extending therebetween, electro-responsive means for switching the communication channels, means for energizing the electroresponsive means for establishing a communication connection between the teletypewriters at two of the stations for the transmission of permutation code signals, and means for deenergizing said electroresponsive means for discontinuing the communication connection and for establishing at the same time another communication connection between teletypewriter at one of the two stationsI and a teletypewriter at another of said stations.

2. A printing te-legraph system including in combination a plurality of subscribers printing telegraph stations each provided with a teletypewriter having a plurality of instrumentalities with means for operating said instrumentalities, a plurality of communication channels extending therebetween, electroresponsive means for switching the communication channels, a circuit for energizing said electroresponsive means for establishing a communication connection between the teletyp-ewriters at two of the stations for the transmission of permutation code signals, and control means for deenergizing the electroresponsive means for discontinuing the communication connection and for establishing at the same time another communication connection between a teletypewriter at one of the two stations and a teletypewriter at another of said stations, said control means including a contact connected into said energizing circuit and means for operating the contact in response tothe operation of a preassigned instrumentality in one of the teletypewriters.

3. A printing telegraph system including in combination a plurality of subscribers teletypewriter stations, a plurality of communication channels extending therebetween, means for connecting two of said stations together in communicative relation, normally unenergized switching means for disconnecting these two stations and for connecting one of the two stations to another of said stations for communication therebetween, a normally open circuit for energizing the switching means, a printing telegraph machine having a plurality of pull bars, and a contact mounted in said printing telegraph machine for operation by one of the pull bars for closing said energizing circuit.

4. A printing telegraph system including in combination a plurality of subscribers teletypewriter stations, a plurality of communication channels extending therebetween, means for connecting two of said stations together in communicative relation, switching means for disconnecting these two stations and for connecting one of the two stations to another of said stations for communication therebetween, a normally open circuit for energizing the switching means, a printing telegraph machine having a plurality of pull bars, a contact mounted in said printing telegraph machine for operation by one of the pull bars for controlling the operation of the switching means, a normally open activating contact mounted in said printing telegraph machine for closing part of the energizing circuit, and means for closing said activating contact.

5. A printing telegraph system including in combination a plurality of subscribers teletypewriter stations, a plurality of communication channels extending therebetween, means for connecting two of said stations together in communicative relation, switching means for disconnecting these two stations and for connecting one of the two stations to another of said stations for communication therebetween, a normally open energizing circuit for energizing the switching means, a printing telegraph machine having a normally open rst contact for closing part of the energizing circuit and a normally open second contact for completing the energizing circuit, and operating means for closing both of the contacts for effecting the energization of the switching means.

6. A teletypewriter communication system including in combination at least three different subscribers teletypewriter stations, a plurality of communication channels extending therebetween, switching means for connecting the rst an-d second of the stations together in communicative relation, a printing telegraph machine having a rst contact and a second contact mounted therein, operating means for operating firstly the rst contact and secondly the second contact for causing the switching means to disconnect these two stations and to connect the first of the two stations to the third station, and means for operating firstly the second contact and secondly the rst contact for causing the switching means to disconnect the rst and third stations and to connect the rst station back to the second station.

7. A teletypewriter communication system including in combination a teletypewriter central oiiice and at least three different subscribers teletypewriter stations, a plurality of communication channels extending from the central oice to the three subscribers stations, switching means for connecting and disconnecting one of said subscribers stations to and from the second and third subscribers stations alternately, a normally open energizing circuit for energizing the switching means', a normally open activating contact for closing part of the energizing circuit, means for closing said activating contact in response to the transmission over the system of a preassigned permutation code signal, operating means, means for operating the operating means in response to a second preas'signed permutation code signal transmitted over .the system after the switching means has been conditioned for operation for causing the switching means to disconnect the first of the subscribers stations from the second of the subscribers stations and connect it to the third of the subscribers stations, and means for operating the operating means in response to a third preassigned permutation code signal transmitted over the system after the switching means has been conditioned for operation for causing the switching means to disconnect the Iirst of the subscribers stations from the third subscribers station and to connect it to the second subscribers station.

8. A teletypewriter communication system including in combination a teletypewriter central oiice and three different subscribers teletypewriter stations, a plurality of communication channels extending from the central oflce to the three subscribers stations, switching means for connecting and disconnecting one of said subscribers stations to and from the second and third subscribers stations alternately, activating means for conditioning the switching means for operation, means for operating said activating means in response to the transmission over the system of a preassigned permutation code signal, operating means, means for operating the operating means in response to a second and a third preassigned permutation code signals transmitted over the system after the switching means has been conditioned for operation for causing the switching means to `disconnect the iirst of the subscribers stations from the second of the subscribers stations and connect it to the third of the subscribers stations, and means for operating the operating means in response to the transmission of the second and third preassigned permutation code signals over the system in reverse order after the switching means has been conditioned for operation for causing the swit-ching means to disconnect the rst of the subscribers stations from the third subscribers station and to connect it to the second subscribers station.

9. A printing telegraph system including in combination a rst printing telegraph machine, a second and third printing telegraph machines, a plurality of circuits for connecting the second `and third printing telegraph machines alternatively to the first printing telegraph machine for communication therebetween, electroresponsive means, control means for controlling the electroresponsive means for connecting the second printing telegraph machine to the first printing telegraph machine for communication therebetween while connecting the third printing telegraph machine into `an idle circuit, and additional control means for causing the electroresponsive means to disconnect the second printing telegraph machine from the first printing telegraph machine and to connect it into an idle circuit while in the same operation disconnecting the third printing telegraph station from its idle circuit and connecting it to the first printing telegraph machine for communication therebetween.

10. A printing telegraph system including in combination a first printing telegraph machine, a second and third printing telegraph machines, a plurality of circuits for connecting the second and third printing telegraph machines alternatively to the rst printing telegraph machine for communication therebetween, and switching means for disconnecting one of the other printing telegraph machines from the iirst printing telegraph machine while in the same operation connecting the other printing telegraph machine to the first printing telegraph machine for communication therebetween.

HORACE JAMES BRITT. 

